The Challenge

And with the mere flick of a switch, it is done. Leaving a dazzling trail
of rainbow colors, the starship Enterprise flashes out of sight
on its way to yet another adventure among the stars. It all seems so easy.
But will star travel ever be that easy and quick? Will it ever prove possible
at all?

Gaze up at the night sky, and there is nothing but a thin layer of air between
you and the stars – nothing, that is, except for countless miles of
empty space. Even the nearest star to Earth, beyond the Sun, lies at the
fantastic distance of 25 trillion miles!

No one can imagine a distance that huge. But if we make a tiny scale model
of everything in space, we can begin to appreciate how far away the starts
are compared to our neighboring planets.

Suppose the Sun has been shrunk down to the size of a pinhead and placed
in the middle of San Francisco. Then Earth would be a speck, too small to
be seen, just 4 inches away. The most remote planet in the Solar System,
Pluto, would orbit, or move around, the Sun at a distance of a little more
than 12 feet. But on the same scale, the nearest star would lie beyond the
city limits, 19 miles away! And that is only the nearest star. Some of the
stars you can see in the night sky would be as far off as Detroit –
more than 2,000 miles distant – while others would be in London, Sydney,
and Moscow.

Speed and Distance

So, could you ever fly to the stars? That depends on whether we can ever
build spacecraft that can cover trillions of miles in much less than a human
lifetime.

Interstellar distances – the gaps between stars – are so great
that astronomers don't usually measure them in mils or kilometers. Instead,
they use light-years. One light-year is the distance that light, speeding
along at 186,282 miles per second, travels in a year. It equals slightly
less than 6 trillion miles. By this reckoning, the nearest star is 4.2 light-years
away.

To break free of Earth's pull of gravity, a spacecraft has to gain a cruising
speed of about 25,000 miles per hour. If it then maintained that speed,
it could reach the planet Mars in about three months. A trip to Jupiter
would last two years, while a direct flight to Pluto would take 10 times
as long. Still, the planets that go around our own Sun are much closer to
us than any other star. At a steady 25,000 miles per hour, the trip to Proxima
Centauri – the nearest star to Earth beyond the Sun – would
take 114,000 years!

Even if we could somehow make our present-decay a thousand times faster,
they still could not reach any other star within an average person's lifetime.
Does that mean star travel will forever remain a dream? Does it mean that
a real starship Enterprise is impossible to build? Certainly, there
are difficult problems that must first be solved. But scientists already
know of several ways in theory to make superfast spaceships. Some of these
new types of spacecraft could approach the speed of light itself. And there
may even be a way of breaking through the light barrier.

Later, we shall explore some of these exciting ideas for possible future
starships. But first, we will see how far we have already progressed along
the road to the stars.